Design Of PDME System Based On FPGA

At present,the meter wave instrument landing system(ILS)used for aircraft landing has many institutional defects,for example,it can only provide a single gliding line in space,which is only suitable for large aircraft take-off and landing;there are only 40 working channels,which is not enough for geographically densely arranged airports;because it works in the meter wave band,it is close to the frequency of FM radio stations and some paging stations,and is vulnerable to interference.The ranging method matched with the ILS system is DME ranging,but the DME ranging error is large.When the weather conditions are relatively bad,the landing of the aircraft depends on the manual operation of the pilot,which makes the application of ILS and DME systems subject to many limitations.Therefore,this paper studies the use of Precision Distance Measuring Equipment(PDME)instead of the traditional ranging system.Firstly,the development background,present situation and future development trend of Precision Distance Measuring Equipment(PDME)are briefly introduced;then the ranging principle of PDME system is introduced,and the composition and technical characteristics of ground and airborne equipment are summarized;then the generation method of PDME pulse waveform and the FPGA realization of communication content are introduced emphatically,and the simulation waveform is given;finally,the hardware circuit is designed to achieve the purpose of engineering realization.The focus of PDME system ranging is pulse.In order to improve the ranging accuracy and minimize the error caused by multipath interference,a rapidly rising pulse front must be adopted,so that the detection reference point can be in a place where there is no multipath interference.Therefore,this paper focuses on the generation of ranging pulses in PDME system through FPGA,and analyzes the causes of errors and the relationship between pulse waveforms and distance errors.At the same time,to encode the transmitted pulse,the purpose of coding is to select the transponder placed in the working area of the interrogator.After coding,only one of the transponders close to the position receives the predetermined coded signal and answers with a certain code.In this paper,paired pulses are used as interrogation signals to change thetime interval between pulses to achieve coding,and the response signal is also encoded by changing the time interval between carrier frequency and pulses.Therefore,this paper studies the communication mode and content between the aircraft and the ground in detail,introduces the communication signal format in different situations,and gives the simulation waveform.